AB0408 DESCRIPTIVE STUDY ON USE OF BIOSIMILARS IN RHEUMATOID ARTHRITIS IN UNIVERSITY HOSPITALS PLYMOUTH, UNITED KINGDOM
Authors: A. Ediriweera, T. Aung, O. Savanovic-Abel
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Rheumatoid arthritis (RA) is a chronic inflammatory disease of unknown etiology marked by a symmetric, peripheral polyarthritis. Treatment of RA should be aimed at reaching a target of sustained remission or Low Disease Activity (LDA) in every patient. [1] Given the heterogenicity of the disease, there are multiple disease modifying anti rheumatoid drugs (DMARDs) available including biologics and biosimilars with different modes of action to achieve disease remission or low disease activity. A biosimilar medicine is a biological medicine manufactured to be similar to an existing licensed "reference" biological medicine, with no meaningful differences from reference medicine in terms of quality, safety or efficacy. However, it has been observed significant number of patients going back on bio-originator drugs complaining either side effects or less efficacy of biosimilar. This study is aimed at looking at real rate of bio-similar (BS) switching back to bio- originator (BO) due to various reasons. <h3>Objectives:</h3> 1)To look for rate of switching back to bio-original and reasons behind 2)Biosimilar persistence rate in RA and side effect profile 3)To look for any association between concurrent use of methotrexate with biosimilar persistence rate. <h3>Methods</h3> Descriptive study was done at department of rheumatology University Hospitals Plymouth (UHP). All patients with the diagnosis of Rheumatoid arthritis, treated with biological DMARDs were screened till October 2019. Data were gathered about switching back to BO from BS and if switched reason for switch, persistence rate of biosimilar, duration of biosimilar, disease activity measured by DAS 28 before and 6 weeks after biosimilar, side effects and concurrent use of methotrexate with biosimilar. Data were analyzed as percentages and chi-square is used to find associations. <h3>Results</h3> Total number of 590 patients with RA on biological DMARDs were screened. Most popular first choice of BS was etanercept (318) followed by rituximab (177), adalimumab (85) and infliximab [9]. Only 19 patients out of 318(5.9%) patients treated with etanercept BS went back to BO due to inefficacy and side effects. 222/318 (69.8%) remained on etanercept. Switching back rate of adalimumab BO was only 9.4% (8/85) while 73% remained on adalimumab BS. (62/85). For rituximab, 9 out of 177 (5.08%) patients went back to original; 6 due to inefficacy and 3 side effects. 147/177(83.05%) remained on BS rituximab. Only one patient out of 9 treated with infliximab went back on original drug due to inefficacy. Commonly observed side effects of BS are infections, allergic reactions, and gastrointestinal disturbances. Average DAS 28 score difference after 6 weeks of commencement of BS was calculated only for adalimumab and etanercept. There was 2.27 reduction of DAS 28 in adalimumab group (from 5.22 to 2.95) while the reduction was 1.67 for etanercept group (from 5.14 to 3.47). Looking at association between persistence rate of BS and concurrent use of methotrexate, only RA etanercept group showed a significant association with a <i>p value</i> of 0.000041. <h3>Conclusion</h3> Significant number of patients with RA are treated with biosimilar in UHP. Re switching to bio-originator is not very commonly seen. Most of the patients could tolerate biosimilar well and persistence rate is impressively high with good response reflected by reduction of average disease activity in studied cohorts. Among side effects infection, allergic reaction and GI side effects are common. Concurrent use of methotrexate showed positive correlation with persistent rate of biosimilar only in one group (RA treated with etanercept) but not others, hence does not give strong ground to the hypothesis that methotrexate minimizes immunogenicity for biosimilar. <h3>Reference</h3> [1]Smolen JS, Landewé RBM, Bijlsma JWJ, et al. EULAR recommendations for the management of rheumatoid arthritis with synthetic and biological disease-modifying antirheumatic drugs: 2019 update; Annals of the Rheumatic Diseases 2020;79:685-699. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.